Abstract

We study the effect of electromagnetically aligning the suspension on the frequency-dependent gain coefficient for energy transfer via NDTWM, and we find that electromagnetic alignment of the particles vastly alters the nonlinear optical characteristics of the suspension. Previous studies focused on static index gratings and predicted a number of novel effects arising from microparticle alignment that manifest themselves in optical phase conjugation. Here we focus on moving optical index gratings and find additional new phenomena that reveal themselves in the gain spectrum for energy transfer via two-beam coupling. Specifically, (1) the magnitude of the low frequency portion of the gain coefficient due to the formation of moving translational index gratings depends on the extent of particle alignment and shape, and the direction of power flow can be reversed. (2) The high frequency portion of the gain coefficient due to the presence of a moving orientational index grating exhibits similar behavior. However, the dynamics associated with reversal of power flow is somewhat different and occurs for different material and electric field parameters.

© 1992 Optical Society of America